def sieve( max ): max_val = int( sqrt( max ) ) s = Set(xrange( 4, max, 2 )) for i in xrange( 3, max_val, 2 ): s.update( xrange( 2*i, max, i ) ) return [ i for i in xrange( 2, max ) if i not in s ]
just for grins, here is the same (mostly) code in haskell
import Data.Set(elems, fromList, member, union)
primeSieve :: Int -> [Int]
primeSieve n = [ prime | prime <- [ 2 .. n ], not $ prime `member` nonPrimes ]
where
evenSet = fromList [4, 6 .. n ]
xIncrements x = [ 2 * x, (2 * x) + x .. n ]
maxVal = floor . sqrt $ fromIntegral n
oddSet = fromList . concat $ map xIncrements [ 3, 5 .. maxVal ]
nonPrimes = union evenSet oddSet
fromList makes a list into a Set. [ x | x <- y, pred ] is analogous to Python's [ x for x in y if pred x ]. The '$' operator removes the need for parens.
foo $ bar baz --> foo (bar baz)
oh and '.' is the function composition operator. _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
